Cryptosporidiosis in immunocompetent patients.

The intestinal protozoan cryptosporidium is known to cause diarrhea in immunocompromised patients, but few cases have been reported in detail in immunocompetent persons. During a 12-month period, we identified cryptosporidium in the stools of 43 immunocompetent patients. The numbers of cases were increased in those under 4 years old and in those from 30 to 39 years old. Of 30 index cases, 23 (77 per cent) were diagnosed in the late summer or the fall. Fifteen of the 43 patients (35 per cent) had other gastrointestinal pathogens, of which only Giardia lamblia was statistically associated with cryptosporidium. In the 28 patients in whom other gastrointestinal pathogens were not identified, the clinical manifestations were predominantly watery, nonbloody diarrhea and, less commonly, abdominal discomfort, anorexia, fever, nausea, and weight loss. The infection was self-limited in all 43 patients. Clustering of cases occurred in a day-care center and in two families. These clinical observations confirm worldwide findings and suggest that cryptosporidium is a relatively common nonviral cause of self-limited diarrhea in immunocompetent persons in the northeastern United States.